In the following, the transponder is characterized as an integrated circuit which is conductively connected to a coil. Transponders of this kind are known and are surrounded by a body to protect against mechanical loads.
Conveyor belts are used in conveyor belt installations and are often several hundred meters long. In daily use, the conveyor belts can be subjected to high mechanical loads and especially to high tension forces. For this reason, tension reinforcement is introduced into conveyor belts subjected to high loads. This tension reinforcement can, for example, comprise high-strength steel cords which are embedded in a special rubber. It is likewise known to configure the tension reinforcement in the form of multi-layered textile inserts. With the tension reinforcement, the mechanical loads to which the conveyor belt can be subjected, can be significantly increased; however, it cannot be precluded that damage can occur to the conveyor belt because of a load which is too high. Especially the connecting region, in which the ends of the conveyor belt are connected to each other, remains a weak location. For this reason, it has already been suggested to check conveyor belts and especially their connecting regions on a regular basis for signs of loosening.
In view of the above, and as disclosed, for example, in German patent application 196 03 578, at least one transponder is introduced into the connecting region of a conveyor belt which transmits a signal to an external transmitter/receiver unit in a first functionally operable state when passing through the operative area of this transmitter/receiver unit. The transponder transfers into a second functionally inoperable state when a critical change in form of the connecting region takes place on the conveyor belt as a result of mechanical tension loads which are too high so that the transponder can no longer transmit a signal to the external transmitter/receiver unit. The absence of the signal is an indication to the external transmitter/receiver unit that a critical change in form is present in the connecting region of the conveyor belt and appropriate control measures are initiated which reduce the tension load in the connecting region of the conveyor belt. This can, for example, be achieved by reducing the load on the conveyor belt. In an extreme case, the conveyor belt can be brought to standstill by the external transmitter/receiver unit.
With the method disclosed in German patent application 196 03 578, critical changes in form of the connecting region of the conveyor belt can be reliably and satisfactorily monitored. However, this method is based on an irreversible destruction of the transponder introduced into the connecting region. For this reason, the method can, after a critical change in form of the connecting region is exceeded, only be carried out again after the destroyed transponder is replaced by a functionally operational transponder. A replacement of this kind introduces costs which are then unnecessary when only changes in length of the connecting region are indicated by the transponder which do not lead directly to damage of the connecting region and therefore to the conveyor belt.